Centaurus A . ... and Kevin Ivarsen ( PROMPT / CTIO / UNC) Explanation: What's the closest active galaxy to planet Earth? ... Forged in a collision of two otherwise normal galaxies, Centaurus A's fantastic jumble of young blue star clusters, pinkish star forming regions, and imposing dark dust lanes are seen here in remarkable detail. ... As in other active galaxies, that process likely generates the radio, X-ray, and gamma-ray energy radiated by Centaurus A . ... NASA Official: Jay Norris. ...